Thrush on new born . ?

My son is 7w old now and still has this thrush that his had since he was 2w old . His doctor prescribed him meds but I swear it’s not helping him . It says to use for two weeks it’s past a week now and no difference. His sister had the same issue when she was a baby and her doctor prescribed me meds and the thrush was gone within a week . And the meds that my son has is different then the one his sister had .

At the same time idk if it’s because I’m breastfeeding him and giving him the bottle . But his mostly breasted now and barely on the bottle . I can tell his getting annoyed by it because he sticks out his tongue out sometimes but other then that his fine .